Cytogenetic and biochemical differences between Apodemus sylvaticus and Apodemus flavicollis, possibly responsible for the failure to interbreed

Biogeography and taxonomy of Apodemus sylvaticus (the woodmouse) in the Tyrrhenian region: enzymatic variations and mitochondrial DNA restriction pattern analysis

“…No such differences have ever been discovered among A. sylvaticus populations. Moreover, the karyotype and the G and Q-banding patterns of the woodmouse are very similar to those of A. flavicollis (the yellow-necked mouse) (Engel et al, 1973). However, Giagia (1985) reports some rare individuals bearing supernumerary acrocentric chromosomes whose significance remains unclear, their occurrence being higher in polluted areas (caused by heavy metals and chemicals).…”

Phylogeny of the genus Apodemus with a special emphasis on the subgenus Sylvaemus using the nuclear IRBP gene and two mitochondrial markers: cytochrome b and 12S rRNA

“…Species within the subgenus Sylvaemus are phenotypically very similar, and traditional morphometrics are often at a loss to distinguish between them Zagorodnyuk, 1996). For this reason, several authors have employed protein electrophoresis (Britton-Davidian et al, 1991;Csaikl et al, 1980;Engel et al, 1973;Filippucci, 1992;Filippucci et al, 1996Filippucci et al, , 2002Gemmeke, 1980;Hartl et al, 1992;Mezhzherin and Zykov, 1991) and traditional cytogenetics (Bulatova et al, 1991;Nadjafova et al, 1993;Zima, 1984) in an attempt to unravel relationships. Unfortunately, similar to morphometrics, cytogenetics were not successful in delimiting species, given the uniformity in karyotypic characteristics of this subgenus.…”

Sex-chromosome heterochromatin variation in the wood mouse, <i>Apodemus sylvaticus</i>

“…The best-studied example of such variation in mammals is the occurrence of so-called giant sex chromosomes originating from heterochromatin amplification in certain species of voles (Diá z de la Guardia et al, 1979;Modi, 1992;Zima and Macholá n, 1995). Variation in the size of the sex chromosomes has also been reported between some species of the Palaearctic genus Apodemus (Engel et al, 1973;Saitoh and Obara, 1986;Obara et al, 1997;Reutter et al, 2001).…”

“…In the karyotype of this species, blocks of constitutive heterochromatin have been shown to occur in various chromosomal locations-centromeric, telomeric, and interstitial (Engel et al, 1973;Gamperl et al, 1982). B chromosomes that are apparently heterochromatic have been recorded occasionally in A. sylvaticus (Zima et al, 1997).…”